Hales Nicole R, Schield Drew R, Andrew Audra L, Card Daren C, Walsh Matthew R, Castoe Todd A
Department of Biology, University of Texas at Arlington, Arlington, TX, USA.
Mol Ecol. 2017 Oct;26(19):5003-5015. doi: 10.1111/mec.14213. Epub 2017 Jul 10.
Research has shown that a change in environmental conditions can alter the expression of traits during development (i.e., "within-generation phenotypic plasticity") as well as induce heritable phenotypic responses that persist for multiple generations (i.e., "transgenerational plasticity", TGP). It has long been assumed that shifts in gene expression are tightly linked to observed trait responses at the phenotypic level. Yet, the manner in which organisms couple within- and TGP at the molecular level is unclear. Here we tested the influence of fish predator chemical cues on patterns of gene expression within- and across generations using a clone of Daphnia ambigua that is known to exhibit strong TGP but weak within-generation plasticity. Daphnia were reared in the presence of predator cues in generation 1, and shifts in gene expression were tracked across two additional asexual experimental generations that lacked exposure to predator cues. Initial exposure to predator cues in generation 1 was linked to ~50 responsive genes, but such shifts were 3-4× larger in later generations. Differentially expressed genes included those involved in reproduction, exoskeleton structure and digestion; major shifts in expression of genes encoding ribosomal proteins were also identified. Furthermore, shifts within the first-generation and transgenerational shifts in gene expression were largely distinct in terms of the genes that were differentially expressed. Such results argue that the gene expression programmes involved in within- vs. transgeneration plasticity are fundamentally different. Our study provides new key insights into the plasticity of gene expression and how it relates to phenotypic plasticity in nature.
研究表明，环境条件的变化能够在发育过程中改变性状的表达（即“代内表型可塑性”），同时诱发可延续多代的可遗传表型反应（即“跨代可塑性”，TGP）。长期以来，人们一直认为基因表达的变化与表型水平上观察到的性状反应紧密相关。然而，生物体在分子水平上如何将代内可塑性和跨代可塑性联系起来尚不清楚。在此，我们使用一种已知具有强烈跨代可塑性但代内可塑性较弱的模糊水蚤克隆，测试了鱼类捕食者化学信号对基因表达模式在代内和跨代的影响。第一代水蚤在有捕食者信号的环境中饲养，在另外两个未接触捕食者信号的无性实验代中追踪基因表达的变化。第一代最初接触捕食者信号与约50个反应基因有关，但在后代中这种变化要大3至4倍。差异表达的基因包括参与繁殖、外骨骼结构和消化的基因；还鉴定出编码核糖体蛋白的基因表达有重大变化。此外，第一代内的基因表达变化和跨代的基因表达变化在差异表达的基因方面基本不同。这些结果表明，参与代内可塑性与跨代可塑性的基因表达程序存在根本差异。我们的研究为基因表达的可塑性及其与自然界表型可塑性的关系提供了新的关键见解。
